US1943578A - Pressure reducing seal for centrifugal pumps - Google Patents

Description

Jan. 16, 1934.

G. E. Blei-:Low r-:r Al. 1,943,578

PRESSURE REDUCING SEAL FOR CENTRIFUGAL PUMPS Filed Feb. 16, 1931 5/ @5 5 54 a2 6@ 57 #rMen/5x Patented Jan. 16, 1934 PRESSURE REDUCING SEAL FOR CENTRIFUGAL PUIVIPS George E. Bigelow, Southgate, and Arthur It. Weis, Huntington Park, Calif., assignors of one-half to Pacific Pump Works, Huntington Park, Calif., a corporation of California Application February '16, 1931. Serial No. 516,064

2 Claims.r (Cl. 286-9) Our invention relates to an improved sealing device and more particularly to a pressure-reducing seal for centrifugal pumps of the hot-oil type.

In certain cracking processes utilized in the refining of petroleum products, it is desirable to be able to circulate large quantities of hot-oil at temperatures ranging from 40G-850 F. and at pressures ranging from below 11,500lb per square inch to above 2,000lb per square inch. By proper design it is possible to secure these pressures by the use of a centrifugal pump, and the present invention relates to a sealing means which not only successfully seals off such large pressures, but, in addition, nds particular utility with such a hot-oil pump, in view of the'fact that it removes any vapors which might otherwise escape through the sealing means and be discharged into the atmosphere, these vapors thus not only creating an explosion hazard, but also contaminating the atmosphere to such an extentv that it is detrimental to the health of the attendants. y

It is an object of this invention to provide an improved sealing means for such a hot-oil turbine pump in Which any vapors escaping therethrough are removed.

A further object of the invention is to provide a sealing means in which the pressure is reduced in a plurality of steps.

Still a further object of the invention is to provide such a packing means in which a fluid is circulated through a chamber communicating with a high-pressure zone through a throttle means, this fluid acting as a cooling medium.

Other objects of the invention lie in the novel details of construction herein disclosed.

While we will particularly describe our invention as applicable to a turbine pump of the hot-v oil type, it is at once apparent that our sealing means is applicable to other installations, and the apparatus to be hereinafter described is illustrated in conjunction With a hot-oil turbine pump merely for the sake of convenience and because this type of sealing means has especial utility with such a pump.

Fig. 1 is a side view of a hot-oil turbine pump incorporating the features of the invention.

Fig. 2 is a Vertical sectional view ofthe intake end of the pump illustrating the details of our sealing device.

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2. l Y

Referring particularly to Fig. 1, the turbine pump provides a shell 10 to which intake and exhaust heads 11 and 12 are connected. The hot oil is supplied to the pump through a pipe 13 communicating -With the head l1, this oil being forced through a passage 14 of the intake head, and passing successively through a plurality of impellers secured to a shaft 15 mounted in impeller chambers of the vpump in any desired manner, these constructional details forming no part of the present invention. The shaft extends through the intake and exhaust heads 11 and 12 and is journalled in bearings 16 and 17, as shown and claimed in certain co-pending applications, the whole pump being supported on asuitable base 18.

It is necessary to seal olf the shaft 15 relative to the intake head and to the exhaust head, and it is in this capacity that our sealing device finds particular utility. For illustrative purposes, We will, however, disclose the constructional details of the sealing device at the intake end of the pump, it being understood that a similar seal is positioned in the exhaust head 12.A .The pressure which must be packed off by each sealing device is relatively large, for if such a hot-oil turbine, pump is used as a circulating pump,'the intake pressure thereof may be only several hundred pounds lower than the exhaust pressure thereof,Y thus requiring the use of high-pressure sealing devices on both the intake and exhaustV ends of the pump.

The shaft 15 forms a part of a rotatable mem.-V ber 20 which, in the preferred form of the invention as shown in Fig. 2, also includes a spacer sleeve 21 Yand a locking sleeve 22 for each sealing device. The spacer sleeve 21 forms a sliding fit on a reduced diameter portion 23 of the shaft and is forced into engagement ,with a shoulder 24 thereof by the locking sleeve 22 which is threaded to the shaft as indicated at 25, this locking sleeve also'closely surrounding the shaft. A key 26 is preferably positioned in a keyway formed in theV spacer sleeve 21 and in the reduced diameter portion 23.

That portion of the head 11 which immediately surrounds the sealing device of ourinvention has been termed a body 30 and provides a cavity 31 in which an insert member 33 is positioned. The insert member forms a sliding t with the Wallsof the cavity 31, but does not completely ll this cavity, leaving a chamber 34 at one end thereof. It is preferable to provide a shoulder 35 on the walls of the cavity 31 against Vvvhich the insert member abuts, this insert member being held in place by a suitable retaining means. In the form of the invention shown in Fig. 2 this retaining means comprises a set screw 38 threaded into a boss 39 of the body 30 and extending into a cavity 40 of the insert member. This insert member may thus be withdrawn into the passage 14 (hereinafter termed a high-pressure region) by withdrawing the set screw 38 after the head 11 is removed. I

The insert member 33 provides a bore 42 which is only slightly larger in diameter than the external diameter of the spacer sleeve 21, so as to provide an annular clearance space 43 forming a primary throttle space communicating with theV high-pressure region and with a chamber 48 formed around the rotatable member 20. The chamber 48 communicates with the chamber 34 through a secondary throttle means formed' by a secondary annular space 49 between the insert member and the spacer sleeve 2l, and similar to the annular clearance space 43. This chamber 48 will be hereinafter termed a primary chamber, the chamber 34 being designated a secondary chamber for the purpose of distinction.

A liquid is circulated throughY theprimaryl chamber 48 by a circulating means best shown in Fig. 3` This circulating means may include a pipe 50 communicating with aligned passages 51 and 52 formed respectively in the body 30 and insert member 33, the liquid entering the primary chamber 48 and flowing around the rotatable member 20 and being withdrawn through aligned passages 53 and 54 formed respectively in the insert member 33 and body 30. A pipe 55 conducts the liquid from these aligned openings.

The flow of liquid is so controlled that the pressure in the primary chamber 48 is less than the pressure in the high-pressure region formed by the passage 14, this being accomplished by the use of valves 56 and 57 positioned respectively in the pipes 50 and 55. This pressure may be -indicated by any suitable means such as a pressure valve 58 communicating with the pipe 50. By properly setting the valves 56 and 57 the desired pressure in the primary chamber 48 may be maintained.

Similarly, it is preferable to circulate a liquid through the secondary chamber 34, and as shown in Fig. 3. This may conveniently be accomplished by the use of a pipe 60 communicating therewith through a passage 61 of the body, the flow through the pipe 60 being controlled by a valve 62. The liquid is withdrawn from the secondary chamber 34 through a passage 64 and through a pipe 65 including a valve 66. Proper control of the valves 62 and 66 permits the maintenance of a pressure in the secondary chamber 34 which is less than the pressure in the primary chamber 48, this pressure being indicated by a gage 66a. The pipes 50 and 60 are preferably supplied with a liquid such as oil or water, and most conveniently may communicate with a highpressure source such as a pipe 67, the valves 56 and 62 reducing this pressure to the desired amount.

The end of the cavity 31 is defined by a ledge 70, best shown in Fig. 2, this ledge also deiining the inner end of a packing chamber 71 in which a packing 72, preferably in the form of rings, is positioned. This packing seals off the pressure in the secondary chamber 34, and preventsv an excessive escape of liquid which might otherwise take place through the annular space 73 defined between the ledge and the rotatable member.

We prefer to position a lantern ring 75 in the packing chamber 71 and dening a' lantern vring chamber 76 in alignment with intake and out- 79 connected to the pipe 67 and including a valve 80, and 1n the preferred form oi the invention we prefer to utilize a discharge pipe 81 communicating with the discharge port 78 and provide a valve 82 which controls the pressure in the lantern ring chamber 76, this pressure being maintained lower than the pressure in the secondary chamber 84 and preferably only slightly This pressure may be indicated by a gage 83. a Any suitable means may loe-utilized for compressing the packing in the packing chamber such as, for instance, a gland 86. In Fig. 2, we have shown this gland as being provided Vwith a discharge passage 37 through which any fluid leaking from the lantern chamber. may pass. v

It will thus be at once apparent that our sealing device seals a high-pressure region from a low-pressure region (in this case the atmosphere) by reducing the pressure in a series of steps. Any number of steps may be utilized, and in certain instances we have found it entirely practical to utilize only the chamber 48 or only the chamber 34, thus providing but a single chamber in which the pressure is maintained at a value lower than in the high-pressure region. This combination of a single chamber may be used with or without the packingf72, and in the latter case the annular'space 73 may be made smaller to further throttle the liquid escaping therethrough in the event that the pressure in the single chamber is above atmospheric pressure.

Regardless of whether one or more of such chambers are utilized, our sealing device is particularly adaptable to high-pressure installations, and especially to hot-oil turbine pumps. It has been found to' be extremely difficult, if not impossible, to maintain a packing of the usual type in a hot-oil pump in view of the eXtreme temperatures involved. The throttle space 43, however, may be easily formed, and is defined by above atmospheric.

metallic surfaces, and thus not being susceptible to deterioration due to wear vor to the high ternperatures involved. Such a throttle space, however, effectively decreases the leakage around the rotatable member, and is subjected to little, if any, wear.

The only fact which prevents the oil from vaporizing at such high temperatures is, of course, the high pressure to which it is subjected and as soon as this pressure is reduced the oil immediately turns into vapor. Thus, it is that the mag:

terial flowing through the primary throttle space 43 into the primary chamber 48 vaporizes and the escape of this yvapor from the pump is'very undesirable. The oil or other liquid circulated through the primary chamber 48 condenses this Vapor and removes the condensate therewith.

'The liquid passing through the chamber 48 thusserves several purposes. In the first place, this liquid increases the pressure in the primary chamber 48 thereby decreasing the pressure diffr@ ferential between this chamber and the highpressure region and thus decreasing the amount of oil which escapes through the primary throttle space 43. In the second place, this liquid condenses any'vapors which enter the chamber 48,

. each of the pipes 50, 60, and 79.

and removes the condensate therewith. In the third place, the liquid which is supplied is relatively cool and serves `to cool the rotatable member in the body 30, thus preventing the outer end of the body 30 from being subjected to high temperatures. This is advantageous both from a standpoint of decreasing the temperature to which the packing 72 is subjected, and also from the standpoint that it prevents transfer of heat to the bearing 16, for instance.

By utilizing the secondary chamber 34, it is possible to maintain the pressure difference between the chamber 48 and the high-pressure region still lower, for the larger the number of steps in which the pressure is decreased, the lower the pressure diierential between each step. The liquid lcirculated through the chamber 34 also serves to cool the shaft and carries therewith any liquid which escapes through the secondary throttle space 49. If any of the oil vapor should not be condensed in the primary chamber 48, it will thus flow to the secondary chamber 34 and be therein condensed. Finally, the pressure maintained in the lantern chamber of the packing serves to reduce the pressure still another Step, it being understood that that portion of the packing '72 which lies to the right of the lantern 75 acts as a throttle means for any liquid moving into the lantern chamber.

It is thus apparent that we are not limited to the particular number of steps utilized, nor are we limited to the particular duid-circulating system shown in Fig. 3. Other forms of apparatus may be utilized for maintaining the pressures in the chambers at their desired values, such, for instance, as a pressure regulator positioned in Nor is it necessary that the liquid circulated through these chambers be derived from a Ycommon pressure source. In some instances it is not necessary that a liquid be used, a gas or other Huid being substituted. This is not, however, as desirable from an economic standpoint as the liquid-circulating system shown.

We claim as our invention:

1. In a sealing device for sealing a rotatable member relative to a body containing high temperature, high-pressure liquid, the combination of walls defining a bore through which said rotatable member extends and being of a greater diameter than said rotatable member whereby said walls are spaced from said rotatable member to dene a throttle space, one end of which communicates with a high-pressure region of said body whereby the hot liquid in said body tends to enter said throttle space; walls defining a primary chamber communicating with the other end of said throttle space; means for supplying a liquid under pressure to said primary chamber; means for withdrawing liquid from said primary chamber whereby at least a portion of the discharge of said throttle space is removed with the liquid supplied to said primary space; walls around said rotatable member and spaced therefrom to define an auxiliary throttle space communicating with and receiving fluid from said primary chamber; walls defining an auxiliary chamber into which said auxiliary throttle space discharges; means for supplying a liquid under pressure to said auxiliary chamber; means for withdrawing liquid from said auxiliary chamber; means for maintaining the pressure in said primary chamber lower than the pressure in said high-pressure region and for maintaining the pressure in said auxiliary chamber below the pressure in said primary chamber; and packing means around said rotatable member for sealing said auxiliary chamber from the atmosphere.

2. In a sealing device for sealing a rotatable member with respect to a body, said body providing a cavity opening on a high-pressure region and through which said rotatable member extends, the combination of: an insert member retained in but being shorter than said cavity to define an auxiliary chamber in one end of said cavity, said insert member providing a bore which is only slightly larger in diameter than the diameter of said rotatable member to define an annular space therearound, the intermediate section of said bore being enlarged to dene a primary chamber, said primary chamber dividing said annular Space into primary and auxiliary throttle spaces, said primary throttle space opening on said high-pressure region and communieating with said primary chamber, said auxiliary 115 throttle space communicating between said primary chamber and said auxiliary chamber; means for circulating liquid through said primary chamber and maintaining a pressure therein which is lower than the pressure in said high- 120 pressure region whereby leakage through said primary throttle space is conducted from said primary chamber; means including a circulating means for circulating a liquid through said auxiliary chamber and maintaining a pressure therein 125 which is lower than the pressure in said primary chamber; and means around said rotatable member for sealing said auxiliary chamber.

GEORGE E. BIGELOW. ARTHUR R. WEIS.

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